A liquid crystal display generally includes a liquid crystal cell, polarizing elements, and retardation plates. In a transmission type liquid crystal display, generally, two sheets of polarizing elements are disposed on the opposite sides of the liquid crystal cell, and one sheet or two sheets of the retardation plates are disposed between the liquid crystal cell and the respective polarizing elements. In a reflection type liquid crystal display, generally, a reflection plate, a liquid crystal cell, a sheet of a retardation plate, and a sheet of a polarizing element are disposed in this order. The liquid crystal cell generally includes a rod-like liquid crystalline molecule layer, two sheets of substrates for sealing it, an electrode layer for applying a voltage to the rod-like liquid crystalline molecules, and alignment film layers for controlling the orientation of the rod-like liquid crystalline molecules. For the liquid crystal cell, there are proposed various display modes according to the difference in the orientation state of the rod-like liquid crystalline molecules, such as TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Super Twisted Nematic), VA (Vertically Aligned), and ECB (Electrically Controlled Birefringence) modes, for the transmission type, and TN, HAN (Hybrid Aligned Nematic), and GH (Guest-Host) modes for the reflection type.
The retardation plates are used in various liquid crystal displayes in order to eliminate image coloration or enlarge the viewing angle. As the retardation plate, a drawn birefringent polymer film has been used in the background art. There has been proposed the use of a retardation plate having an optically anisotropic layer formed of liquid crystalline molecules on a transparent support in place of a retardation plate formed of a drawn birefringent film. The liquid crystalline molecules have various orientation forms. For this reason, the use of the liquid crystalline molecules enables realization of the optical properties not obtainable with a drawn birefringent polymer film.
The optical properties of the retardation plate are determined according to the optical properties of the liquid crystal cell, specifically, the difference in display mode as described above. The used of the liquid crystalline molecules enables manufacturing of retardation plates having various optical properties adaptable to various display modes of the liquid crystal cell. As the liquid crystalline molecules, generally, rod-like liquid crystalline molecules or discotic liquid crystalline molecules are used. As the retardation plates using liquid crystalline molecules, the ones adaptable to various display modes have already been proposed. For example, retardation plates for the TN mode liquid crystal cell are described in each specification of JP-A-6-214116, U.S. Pat. No. 5,583,679, U.S. Pat. No. 5,646,703 and GP-A No. 3911620A1. Whereas, retardation plates for the IPS mode or FLC mode liquid crystal cell are described in JP-A-9-292522 and JP-A-10-54982. Further, retardation plates for the OCB mode or HAN mode liquid crystal cell are described in each specification of U.S. Pat. No. 5,805,253 and WO96/37804. Still further, retardation plates for the STN mode liquid crystal cell are described in JP-A-9-26572. Then, retardation plates for the VA mode liquid crystal cell are described in Japanese Patent No. 2866372.
Most of the discotic liquid crystalline molecules heretofore used for retardation plates are 2,3,6,7,10,11-hexa{4-(4-acryloyloxybutyloxy)benzoyloxy}triphenylene and derivatives thereof Further, examples using other discotic liquid crystalline molecules have been also reported. However, in any case, the wavelength dispersion value is higher than that of the compound represented by the compound (A).
However, a retardation plate has been required to have various wavelength dispersion values according to the intended use. Particulary, in recent years, the one with a low wavelength dispersion value has become in demand. For example, taking a λ/4 plate as an example of the retardation plate, a retardation plate using liquid crystalline molecules having a small wavelength dispersion value is higher in performances than the plate using liquid crystalline molecules having a large wavelength dispersion value when comparisons are made for all the wavelengths in the visible region.